If the system came with a CD, I assume it came with a CD key as well. If
yes, try doing a repair install and input the product key. If that doesn't
work, it's possible the person who had the system previously may not have
had a legit version of XP:
NOTE, while a repair install should leave your data files intact, if
something goes wrong during the repair install, you may be forced to start
over and do a clean install of XP. If you don't have your data backed up,
you would lose your data should that eventuality occur. Also note, if it
doesn't accept the product key, assuming it was properly typed, that's a
sign the product is invalid.
Boot from the CD. If your system is set to be able to boot from the CD, it
should detect the disk and give a brief message, during the boot up, if you
wish to boot from the CD press any key.
Once you have pressed a key, setup should begin. You will see a reference
asking if you need to load special drivers and another notice that if you
wish to begin the ASR (Automatic Recovery Console) depress F2. Just let
setup run past all of that. It will continue to load files and drivers.
Then it will bring you to a screen. Eventually, you will come to a screen
with the option to (1) setup Windows or (2) Repair Windows Installation
using the Recovery console.
The first option, to setup Windows is the one you want and requires you to
press enter. When asked, press F8 to accept the end user agreement. Setup
will then search for previous versions of Windows. Upon finding your
version, it will ask if you wish to Repair your current installation or
install fresh. Press R, that will run a repair installation. From there
on, follow the screens.
If you only have a recovery CD, your options are quite limited. You can
either purchase a retail version of XP will allow you to perform the above
among other tools and options it has or you can run your system recovery
routine with the Recovery CD which will likely wipe your drive, deleting all
files but will restore your setup to factory fresh condition.
